In contrast to animals, plants can continuously cease and resume growth. This flexibility in their architecture and growth patterns is partly achieved by the action of plant hormones. Plant hormones are structurally diverse compounds that act usually at nanomolar concentrations and include five groups of the so-called “classic” hormones, namely auxins, cytokinins (CK), gibberellins (GA), abscisic acid (ABA) and ethylene. Jasmonates (JA), salicylates (SA), strigolactones (SL), brassinosteroids (BR), polyamines and some peptides were recognized as new families of plant hormones. To date, auxin, CK, GA, SL, BR and polyamines are identified as the major developmental growth regulators, whereas ABA, ethylene, SA and JA are often implicated in stress responses. Recent studies support the contention that hormone actions build a signaling network and mutually regulate several signaling and metabolic systems, which are essential both for plant development and plant responses to biotic and abiotic stresss. Some examples include auxin and GAs in growth regulation; CKs, auxin, ABA and SL in apical dominance; auxin and BR in cell expansion; ethylene and CKs in the inhibition of root and hypocotyl elongation; ethylene, ABA and GAs in some plant stress responses; or SA, JA and auxin in plant responses to pathogens, to name just a few of the reported hormonal interactions. Although earlier work greatly advanced our knowledge of how hormones affect plant growth and development and stress responses focusing on a single compound, it is now evident that physiological processes are regulated in a complex way by the cross-talk of several hormones. In this Research Topic, we aim at collecting a comprehensive set of original research and review papers focused on hormonal crosstalk in plants.
In contrast to animals, plants can continuously cease and resume growth. This flexibility in their architecture and growth patterns is partly achieved by the action of plant hormones. Plant hormones are structurally diverse compounds that act usually at nanomolar concentrations and include five groups of the so-called “classic” hormones, namely auxins, cytokinins (CK), gibberellins (GA), abscisic acid (ABA) and ethylene. Jasmonates (JA), salicylates (SA), strigolactones (SL), brassinosteroids (BR), polyamines and some peptides were recognized as new families of plant hormones. To date, auxin, CK, GA, SL, BR and polyamines are identified as the major developmental growth regulators, whereas ABA, ethylene, SA and JA are often implicated in stress responses. Recent studies support the contention that hormone actions build a signaling network and mutually regulate several signaling and metabolic systems, which are essential both for plant development and plant responses to biotic and abiotic stresss. Some examples include auxin and GAs in growth regulation; CKs, auxin, ABA and SL in apical dominance; auxin and BR in cell expansion; ethylene and CKs in the inhibition of root and hypocotyl elongation; ethylene, ABA and GAs in some plant stress responses; or SA, JA and auxin in plant responses to pathogens, to name just a few of the reported hormonal interactions. Although earlier work greatly advanced our knowledge of how hormones affect plant growth and development and stress responses focusing on a single compound, it is now evident that physiological processes are regulated in a complex way by the cross-talk of several hormones. In this Research Topic, we aim at collecting a comprehensive set of original research and review papers focused on hormonal crosstalk in plants.